Chlorinated, carboxyl group-containing polyolefins are useful, for example, as primers or as coatings for a variety of substrates, such as for example, polyolefin substrates. While such materials may have good properties of toughness, flexibility and chemical resistance when used in coating applications, the adhesion of such coatings to the desired substrate is frequently poor, and consequently conditions such as solvent contact, high humidity and the like cause release of the coating from the substrate. It would, therefore, be an advance in the art to provide modified chlorinated polyolefins capable of forming primers or coatings which have good adhesion to substrates, and which, in addition, have good heat stability, toughness, flexibility and chemical resistance.